It has long been known that the Chrysler LA series small-block engine can be a real powerhouse if the proper combination of parts is used during the build, and that cylinder head choice is an important factor when it comes to engine power. Even more important than cylinder head selection, however, is the work that goes into those cylinder heads. While many factory and aftermarket cylinder heads can make decent power right out of the box, power potential can be greatly improved by properly performed port and combustion chamber work as well as a good multi-angle valvejob. Unfortunately, if port work is done improperly, there can be great expense with limited benefit in terms of real engine power. Luckily, there are companies like Hughes Engines that have done their research, providing cylinder head modifications that are not only cost effective, but have proven results in terms of cylinder head flow, torque, and horsepower. This month we'll follow along as the Hughes team discusses cylinder head theory, and applies what they've learned to Edelbrock's popular Performer RPM line of small-block Mopar cylinder heads.
Any engine can benefit from cylinder head air flow increase, whether it comes from a custom valve and seat job, bowl porting, or all-out port and combustion chamber work. But when considering how far to go with the heads, an engine builder has to decide what gives the most bang for the buck. The cost of ported heads directly relates to how much work is put into the cylinder heads, and at some point cost can go way up with limited benefit which is called the point of diminishing returns. What Hughes has figured out is that the most beneficial cylinder head work actually involves increasing flow at the low and mid valve lifts, because it benefits the total air flow twice, once during valve opening and again as the valve is closing. Porting for flow at maximum lift can have benefits, but since the valve is only at max lift for a short period of time, contribution to total air flow isn't nearly as beneficial as porting for maximum flow at low and mid-valve lift.
01 The Edelbrock cylinder head for the small-block Mopar offers several advantages over f
02 After being treated to Hughes' CNC Super Prepped headwork, you can clearly see the dif
03 The out-of-the-box Edelbrock heads offer a good, multi-angle valvejob. Hughes Engines'
This is not to say that you shouldn't port for the best flow at max lift, but if you're on a budget, you'll see higher power and torque improvements by working the cylinder head for the low- and mid-lift portions of valve travel. Also, if this work is done properly, the head can be fully CNC or hand ported at a later time, to improve flow at maximum valve lift if desired. To demonstrate this theory, Hughes applied their CNC Super Prepped Heads program to a set of the popular Edelbrock Performer cylinder heads for the Chrysler small-block engine.
Hughes Engines has found that the most important area of the port is the valve seat and the one half inch area before and after the seat. The actual valve seat and the angles and widths are the most critical area and receive as much attention during research and development as the rest of the entire port, so they begin any port job with the seat. The intake seat is generally comprised of a number of special angles and widths, and will vary depending on the configuration of the port and valve. Hughes specifically designs the angles and widths of the intake valve seat to improve the low- and mid-lift air flow and wet flow of the head. Don't be confused, however, that the low- and mid-lift improvements only improve low- and mid-range power. Improving flow at these lifts will improve power at all RPM levels.
04 Valve seat angles and widths are important for low- and mid-lift flow increases. Hughe
05a While the Edelbrock cylinder head has better intake ports than that of factory small-
05b These modifications can be worth up to 30 horsepower when the heads are bolted onto a
The valve seat on the exhaust side is equally important to improving air flow, but a slightly different technique is used. Along with the varying angles and widths of those angles, the exhaust seat also benefits from a radius, or curve, along with the angle cuts. After customizing the seats of the intake and exhaust valves, Hughes then moves to the area below the seat called the throat, which transitions into the bowl of the port. The area above the seat is blended into the combustion chamber. Modifications are all dependent on the design of the head, and through testing Hughes knows which heads require certain modifications, including laying back the wall of the chamber directly across from the intake valve and unshrouding the valves themselves.
It is only through testing with a flow bench that determines which modifications are beneficial and which are a waste of time and money. Up to about .350- to .400-inch of valve lift Hughes has determined that the valve and seat angles have the greatest affect, and that the port size and shape only start to affect flow above .400-inch lift. A novice mistake when porting cylinder heads is to concentrate on improving flow at maximum lift, which often sacrifices flow at low and mid-lifts. Hughes attempts to improve total flow across the board, concentrating on improving flow in the "area under the curve," which means more flow at each lift point, not just at maximum valve lift.
The small-block Edelbrock cylinder head in its stock configuration will flow some 40 more cubic feet per minute (CFM) of air more than iron LA cylinder heads like the X or J castings. They also have smaller combustion chambers and a double quench area, which is conducive to making extra power. Hughes treats the Edelbrock head valve seats to a multitude of proprietary angles and widths when cutting the seats--they have found to improve flow at all lift points, or "under the curve." Hughes then CNC machines the chambers of the head to unshroud the intake valve, which encourages better wet flow in the chamber.
06a Hughes' CNC Super Prepped system also greatly benefits the exhaust side of the cylind
06b...with improved flow numbers thanks to valve seat and port work.
07 CNC porting isn't your only option for your heads. Hughes offers additional modificati
By removing restrictions in the ports to improve low- and mid-lift flow, the flow volume can increase to the point that areas of the port that weren't initially a problem can become a problem. This can cause high-lift flow to stagnate at some point, which is corrected by more extensive port work. Again, the sky is the limit here as it takes a lot more work to improve the high-lift flow numbers, without as much total flow gain as the low- and mid-lift improvements. At this point, fully CNC machining the ports and installing larger 2.08-inch intake valves remove the remaining restrictions, but the cost goes up. To get really exotic, Hughes can also move the intake pushrod over some .200 inch, but for most applications budget constraints make this additional work not very cost-effective for most street/strip applications since special offset pushrods are required.
So how much more power do the Hughes CNC Super Prepped heads give when compared to out-of-the-box cylinder heads? This depends on how the engine is built. For example, a 360 small-block with a mild cam and good dual-plane intake, 10.5:1 compression, and headers will gain approximately 30 additional horsepower. Increase displacement to 408 cubic inches, however, and gains could be as high as 50 more horsepower with a substantial improvement in torque as well.
As the charts clearly show, Hughes' research has paid off with big gains in air flow at the low- and mid-lift range. Double-digit flow gains equate to more engine power, and a small-block engine that can produce torque and power numbers more generally associated with Mopar big-block engines. We encourage you to contact Hughes Engines to discuss cylinder head work for your next small-block project, we're sure you'll agree that more torque and horsepower will make your Mopar more fun to drive, though you might need to budget more money for frequent rear tire replacement!
- Edelbrock small-block Mopar Cylinder Heads - $1,439
- CNC porting by Hughes Engines: Price varies depending on extent of work. Call for details.
Out of Box Test
|Intake CFM||Exhaust CFM w/o pipe|
|Lift||INT CFM||Flow Gain CFM||EXH CFM w/o pipe||Gain CFM|
The charts clearly show the mid-range benefit of Hughes Engines' CNC Super Prepped cylinder heads, as air flow is improved on both the intake and exhaust side. What do these numbers equate to? How about 30 to 50 additional tire-frying horsepower, depending on the size and specifications of your small-block.